Don't use stale document capture user ids for effective_user

app/controllers/concerns/effective_user.rb

@@ -1,7 +1,15 @@
 module EffectiveUser
   def effective_user
     return current_user if effective_user_id == current_user&.id
-    return User.find_by(id: effective_user_id) if effective_user_id
+
+    user = User.find_by(id: effective_user_id) if effective_user_id
+
+    if user.nil?
+      session.delete(:doc_capture_user_id)
+      return current_user
+    end
+
+    user
   end
 
   private

spec/controllers/concerns/effective_user_spec.rb

@@ -14,6 +14,31 @@
       it 'returns nil' do
         expect(subject).to be_nil
       end
+
+      context 'with valid doc capture session user id' do
+        before do
+          session[:doc_capture_user_id] = user.id
+        end
+
+        it 'returns session user id' do
+          expect(subject).to eq user
+        end
+      end
+
+      context 'with invalid doc capture session user id' do
+        before do
+          session[:doc_capture_user_id] = -1
+        end
+
+        it 'returns session user id' do
+          expect(subject).to be_nil
+        end
+
+        it 'deletes the session key' do
+          subject
+          expect(session).not_to include(:doc_capture_user_id)
+        end
+      end
     end
 
     context 'non-existent user' do
@@ -22,23 +47,39 @@
       end
     end
 
-    context 'logged out with doc capture session user id' do
+    context 'logged in' do
       before do
-        session[:doc_capture_user_id] = user.id
+        stub_sign_in user
       end
 
       it 'returns session user id' do
         expect(subject).to eq user
       end
-    end
 
-    context 'logged in' do
-      before do
-        stub_sign_in user
+      context 'with valid doc capture session user id that is not the logged-in user' do
+        let(:doc_capture_user) { create(:user) }
+
+        before do
+          session[:doc_capture_user_id] = doc_capture_user.id
+        end
+
+        it 'returns doc capture user id' do
+          expect(subject).to eq(doc_capture_user)
+        end
       end
 
-      it 'returns session user id' do
-        expect(subject).to eq user
+      context 'with invalid doc capture session user id' do
+        before do
+          session[:doc_capture_user_id] = -1
+        end
+
+        it 'returns logged in user' do
+          expect(subject).to eql(user)
+        end
+
+        it 'deletes the session key' do
+          expect { subject }.to(change { session[:doc_capture_user_id] }.to(nil))
+        end
       end
     end
   end